The invention relates to an arrangement for the electrostatic coating of objects with liquid or powdery coating material.
According to a previous concept, such an arrangement consists of
A hollow pipe, PA1 An atomizer nozzle fed with coating material by a supply line running through the barrel of the gun and located at the termination of the gun barrel, PA1 An electrode for charging the atomized material, which electrode is connected to a high voltage source by way of a current-limiting resistor and a high voltage cable running through or on the gun barrel, and PA1 An elongated body of insulating material running essentially parallel to the longitudinal axis of the gun barrel, which body is attached on the gun barrel and carries the electrode (preferably a metal needle, the free end of which is located at a distance from the nozzle of the gun barrel.
The atomizer gun according to this previous concept, (as disclosed in Luderer et al. U.S. patent application Ser. No. 456,827, filed Apr. 1, 1974, entitled "Improvements in Electrostatic Coating" and the disclosure of which is herein incorporated by reference) is distinguished by providing a particularly good electric charge for the coating material, even whenever the coating material has a relatively high conductivity as is the case especially with the modern water paints. In practice, however, it turned out that, especially in the case of an extended operation of the spraying gun, fouling of the electrodes as well as of the electrode carrier can occur as a result of particles of the color pigment. It is true that the electrode of this earlier concept is not directly in the jet of paint emanating from the atomizer nozzle. However, as a result of the arrangement of the electrode at a distance in front of the atomizer nozzle, one cannot prevent individual particles of the color pigment from reaching the electrode or the electrode carrier. Thus, after a certain time, a film of coating material will develop on these elements. Therefore, it was necessary to clean the gun at certain intervals. This leads to short interruptions of the operating process.